A conventional occupant protection activation device includes: two front sensors disposed at a vehicle's front-end; a safety or saving-determining circuit for detecting a signal from each of the front sensors to make a safety or saving determination; and a microcomputer for determining crashing of the vehicle, based on the output of the front sensors and a G sensor disposed at a location spaced from the front sensors. When the safety-determining circuit determines that the front sensor has detected a collision, the circuit inputs a signal indicating that the collision is detected to an AND circuit. At that time, the microcomputer that receives the detected signal of the G sensor outputs a signal, which determines an occurrence of the collision, to the AND circuit. The AND circuit, which received these signals, opens the gate thereof, and thereby a squib is supplied with a current to activate the air bag. On the other hand, when the front sensors does not detect any collision, but only the G sensor detects a collision, the gate of the AND circuit is not opened. Therefore, the squib is not supplied with current, and the air bag is not activated. The detection of the collision, made by the G sensor in such a case is judged to be a malfunction by the noise, and thereby the misoperation of the air bag is prevented. Thus, the microcomputer of the occupant protection activation device makes a safety determination such that the misoperation thereof is prevented, and determines whether the air bag is to be activated, based on the detection signals outputted from the plurality of sensors (for instance, see JP-A-2003-237529).
Patent reference 1: JP-A-2003-237529 (page 4, FIGS. 2 and 3)
The conventional occupant protection activation device has been arranged as mentioned above. As a result, it becomes difficult for the determining means such as the microcomputer determining on occurrence of collision, to make a proper collision determination in connection with the safety determination for preventing the malfunction, when the connection between the determining means and the sensors disposed at the vehicle's front-end is broken by the collision. For this reason, there is a problem that, when the vehicle crashed, the activation of the occupant protection apparatus becomes difficult.
The present invention has been accomplished to solve the above-mentioned problem. An object of the present invention is to provide an occupant protection activation device that activates the occupant protection apparatus even when the sensor disposed at the vehicle's front-end is disconnected therefrom by the collision, while making the safety determination for preventing the malfunction thereof.